MEPS 452:119-130 (2012)  -  DOI: https://doi.org/10.3354/meps09624

ABSTRACT: Present genetic patterns of marine organisms not only result from historical and contemporary ecological factors, but also from anthropogenic activities. Disentangling the relative effects of these factors can provide valuable insights into management and protection of exploitable species. The commercially important marine clam Tegillarca granosa is representative of species that are translocated within East Asia for coastal aquaculture purposes. We conducted a nucleotide sequence analysis of mitochondrial cytochrome c oxidase subunit I and nuclear internal transcribed spacer 1 markers in T. granosa to investigate its genetic diversity and distribution in 2 marginal seas (the East and South China Seas) of the northwestern Pacific. Based on phylogenetic inferences, we identified 2 evolutionarily significant units (ESUs) with high genetic distance between them for both markers. The high genetic distance may be associated with the historical isolation of the marginal seas during low sea level periods. One ESU was widely distributed in both seas, whereas the other was restricted to 2 disjunct localities in the South China Sea. Based on the isolation by distance analysis (p = 0.068) and comparison of patterns of co-occurring species, this pattern appears to be mostly attributable to the human-mediated translocations among coastal waters rather than natural range expansion. Furthermore, from a conservation viewpoint, the southern ESU is now facing high extinction risk because of mitochondrial introgression and smaller, fragmented populations; consequently, immediate proper management is required to protect the endangered populations representing this lineage.

KEY WORDS: Population genetics · Aquaculture species · Evolutionarily significant units · ESUs · Marginal sea · Human activity · Genetic conservation · East Asia